In a large, heavy-bottomed saucepan heat the oil over medium-low heat. Add onion and cook until tender. Add garlic and season well with salt and pepper, cook until fragrant.

Add the tomatoes and thyme, turn heat up to medium and cook about 5 minutes, stirring often.

Add broth and basil. Season again with salt and pepper. Bring to a simmer and cook 25 minutes.

Puree with an immersion blender or carefully remove to a stand blender or food processor to puree until smooth (put a dish towel over the lid of the blender and hold down - the steam can blow the lid off).